Air conditioning apparatus



F. MANNING Er Al. 2,086,385 AIR CONDITIONING APPARATUS' Filed oct. 2,1955 4 sheets-sheet 1 NNW m Ar i m ik F July 6, 1937. I

1N VENTORS July 6, 1937. F. MANNING Er AL 2,086,385

AIR CONDITIONING APPARATUS Filed 001:. 2, 1935. 1 4 Sheets-Sheet 2INVENTORS Lw-MLM Mr I BYM my@ 1s, am

7&5; ATTORNEY.

July 6, 1937. F. MANNING ET AL 2,086,385

AIR CONDITIONING APPARATUS Filed Oct. 2, 1935 4 Sheets-Shn-z'e'fl 3ATTORNEY.

ya l lNyENToR BY Q6. CM@

July 6, 1'937. -F. MANNING ET AL 2,086,385

AIR, CONDITIONING APPARATUS .4 Sheets-Sheet 4 Filed Oct. 2, 1935 Ia Pllll .mf

RNEY.

S i ,i LNVENTOR [l w ATTO Patented July 6, 1937 UNITED STATES PATENTOFFICE I AIR lC-NDITIONING APPARATUS Fowler Manning, Bronxville, andRobert D. Lambert, North Pelham, N. Y., assignors/ to American RadiatorCompany, New York, N. Y., a corporation of New Jersey ApplicationOctober 2, 1935, Serial No. 43,204

5 Claims. (Cl. 2611) This invention relates to. methods of conditioningair in heated room spaces and more particularly to a method of providingproper humidity conditions in room spaces during` the heating g turebeing raised. As the outside air is the ultimate source of all of theair in the room, there is always a deciency of moisture in the heatedroom spaces during the heating season.

The optimum range of relative humidity values for room spacesof hou'sesduring" the heating .season is generally understood to be between 30%and 70%. If no means are provided foradding moisture to the room spaces,the actual relative humidities will fall well below the 30%. This, ofcourse, will depend upon the` prevailing outside climatic conditions;the number of people occupying the room spaces and the amount ofmoisture supp-lying operations suchvas cooking, washing, bathing, etc.,done in the house.

It is an object of the present invention to provide an improved,dependable and inexpensive method of providing a proper humidity of theair in room spaces throughout the range of prevailing outside dry -bulbtemperatures during the heating season, without objectionablecondensation -of moisture on the inside surfaces of the windows andother surfaces most readily affected by the dry bulb temperature oftheoutside air, and without the use of humidity responsive controlinstruments. The invention consists in the series of-steps forming themethod more fully described here- `inafter, and the novelty of whichwill be paticularly pointed out and distinctly claimed.

In the accompanying drawings, to be taken as a part oflthisspecification, we have illustrated two alternative forms of apparatusfor performing the novel steps of our method, in which drawings:

A Fig. 1 is a fragmentary vertical sectional view of a conventionaldwelling house,.showing apparatus installed therein which performs theseveral steps of our improved method;

Fig. 2 is a horizontal sectional view taken on the line 2-2 ofFig. 1,and showing a portion of the aprniratusl for performing thesteps of ourmethod;- l

Fig. 3 is a `vertical sectional viewtaken on the line 3--3 of Fig. 1,and also showing'a'portion of the apparatus;

Fig. 4 is a perspective view of "an"y alternative form of apparatus forperforming the Vsteps oi.' our improved method; and I y Fig. 5 is .agraph showing bya-ourve the actual humidityv conditions maintained overa'inormal range of outdoor temperatures, in ,the room spaces of aconventional dwelling house vwhere our improvedv method was practiced,and also showing by a curve the amount of humidity lthat can bemaintained without deposition of` moisture on the windows of that housefor the same range tof outdoor temperatures.

In accordance with one specific aspect of our invention, our improvedmethod comprises supplying heat to the air in a room space to maintainthe dry bulb temperature of the air contained therein within acomfortable range; withdrawing from the room space a predetermined xedquantity per unit of time of the heated air; taking from the outside aira predetermined fixed quantity'per unit of time of air at its prevailingdry bulb temperature; mixing the withdrawn air with said quantity ofoutside air; increasing the humidity of the mixture by an amount 4,whichis' a predetermined substantially fixed part of the diierence betweenthe amount of moisture in grains per pound the mixture holds p rior tohav- ,ling its humidity increased and the amount of moisture the mixturecould" hold if saturated at its wet bulb temperature, so that.thehumidii'led mixture has at all times relative humidities which varydirectly as a function of the dry bulb temperature of the outside air;increasing the 'dry bulb temperature of the humidied mixture to a ,pointwhere its admission to the .room space will not result in discomfort tothe occupants;

and introducing the heated and humidied mixture intol the room. Byperforming the method steps as just outlined, the air in the room spacemay be always maintained at a comfortable dry bulb temperature and theair will always contain a proper, comfortable and healthful amount ofmoisture, which amount is automatically varied with the changing outsidedry bulb temperatures so that -moisturein objectionable amounts willnotbe;

The steps of our improved method may be carried out by a variety ofvapparatus without departing from the spirit of the present invention. Inthe drawings, we have illustrated two forms of apparatus which we havefound to operate effectively in maintaining the proper condition of theair in room spaces.

Referring rst to apparatus disclosed in Figures 1 t o 3, inclusive, itwill be observed that we have shown such apparatus as installed in aconventional dwelling house which includes a room space I0 dened in partby an outside wall II, an inside wall I2 and a floor I3. A window I4 isprovided in the outside wall II. Beneath the room I0 is a basement spaceI5 dened in part by side walls I6 and a oor I'I.

In accordance with one aspect of our invention, we have providedapparatus for maintaining the dry bulb temperature of the room spacewithin a comfortable range to the individuals occupyingsuch space.'I'his apparatus is shown as being a conventional oil red boiler unit I8having an off-take 'steam main I9 connected by means of a pipe 20 to aradiator 2| installed within the room space. end of the radiator with areturn main 23 leading to the boiler I8. We have shown a thermostat 24mounted on the inside wall I2 and operating to control theoperation ofan oil burner (not shown) disposed within the lower portion of theboiler unit I8. The heating apparatus shown is well known and needs nofurther explanation.

Other -forms of heating apparatus may be used without departing from thescope of the present invention. 'I'he reference character 30 indicatesan apparatus which draws in a mixture-of` room air and outdoor air;lters the mixture; humidifles the mixture; and increases the dry bulbtemperature of the mixture above that of the room and then forces suchmixture into the room at a substantially xed' volume rate.

'Ihe apparatus 30 comprises an outer casing 3I having upstandingdeiining Wal1s32 and a vertical partition wall 33 dening a U-shapedpassage for the ilow of mixture therethrough. 'Ihe v partition 33divides the casing 3I into a down coming leg 34 and an up-going leg 35.

Arranged above the apparatus 30 is a manifold casing 36 which may besuspended from the basement ceiling and is divided by a verticalpartition 31 into an air inlet chamber 3 8 and an air outlet chamber 39(see Fig. 2), lwhich communicate,

respectively, with the down-coming leg 34 andl the up-going leg 35 ofthe apparatus 30. A ilexible section connects the manifold casing 36with the apparatus 30' and the sectiony 40 is also provided with avertical partition 4I which is so arranged with respect to the'partition 31 and the partition 33 as to provide the connection justexplained between the casing 36 and the apparatus 30. The exible sectionmay be formed of any suitable material, such for example, as can,

vas which may be readily cut to' suit the partlcular distance betweenthe suspended manifold 36 and the apparatus 30 resting on the oor of the`basement. The canvasl also .functions as a sound deadening means. y

'rne inlet chamber sa is provided with piu- A pipe 22 connects thereturn i 2,086,385 z r the inlet chamber ss. The other three inletopenings 42 are connected to the room spaces to be humidied by ducts 44communicating with grille- `covered openings 46 in the floor of the roomopenings 52 through the floor of the room spaces.`

A damper 53 is disposed within each of the inlet openings 42 of theinlet chamber 38, and are operated respectively, by suitable lever arms54 arranged on the outside of the respective'flange portion 43. Byregulating the dampers 53, the proportions of outside air and room` airdrawn into the mixing inlet chamber 38 may be varied. As will laterappear, the proper proportions are first determined and the dampers thenremain in their selected positions, without further adjustment beingrequired.

Disposed across the upper portion of the downcoming leg 34 of theapparatus 30 are a pair of lters 55 which are suitably arranged in theform of an inverted V and function to take outof the incoming airmixture substantially all of the foreign matter and dirt entrainedtherein.

Arranged below the lters 55 is a humidifying chamber 56 which forms apart of the down-coming leg 34 and has installed therein a plurality ofspray nozzles 57 suitably connected to the city water supply by a pipe58. In the extreme lower lower end of the down-coming leg 34 and extendsentirely across the leg 34 so that all of the air mixture passestherethrough.

'I'his eliminator 60 may be constructed in any suitable fashion and ofany suitable material. 'I'he eliminator shown comprises a relativeshallow rectangular frame 6I havingk its opposite sides formed Aofspaced metallic screens 62, between which is disposed a suitablevaporizing and moisture eliminating mat'63; suchl for example, as layersof spun glass,` metal wool, or the like. The mat is so constructed as toprovide.a multitude of interstices and tortuous passages for the airowing therethrough. The surfaces of the mat are kept wet by water fromthe sprays, and the air in passing therethroughcontacts with the exposedsurfaces-of the water particles on the surfacosof the mat and effectsevaporation of the water and humidiilcation of the air in a manner wellknownin the art. Due t'o the balding effectl caused by the ltortouspassages,l any Ifree moisture entrainedin the air mixture will be takenout land will ow downward through the mat and into a sump 64. A suitabledrain 64aI is4 provided for conducting away the excess water.

The sprays may be adjusted to vary ftheir humidifying characteristicsand thereby Kvary the extent to which the mixture is humidifled. Thehumidifying characteristics are'temperature,

pressure, flow and degree of neness of the spray; and, with theexception of temperature, these characteristics may be varied bysuitable regulating screws 65 disposed on the upper end of each of thenozzles, and also by varying the pressure of the water against thenozzles by regulating a suitable Valve 66 in the pipe 58 connected tothe city water supply line. As will later appear, when the desiredvalues of these characteristics are once determined, they remain fixedduring the operation of the apparatus. 'I'he temperature of the citywater will, of course, vary within a small range, but the range is sosmall that its eifect on the operation of the method will not makesufcient diiference to justify its regulation.

Arranged within the lower portion of the upgoing leg 35 of the apparatus30, is a blower B1, comprising a casing B8 and a rotating element 69.The casing 68 is provided with a pair of inlet openings 10 communicatingwith the space 1I on the down stream side of the eliminator 60, therebeing one opening through each side of the casing 68. The casing B8 isprovided with an outlet opening 'l2 connecting with a diverging passageI3 which forms a part of the up-going leg 35 of the apparatus. ablydriven by an electric motor which is connected by a belt 'I6 with apulley on the shaftof the rotating element.

Arranged across the upper end of the up-going leg 35 is a radiator I8consisting of a plurality of pipes 19 with fins 80 secured thereto forthe purpose of promoting heat transfer. The radiator 'I8 is connected tothe supply and return mains I3 and 23 of the boiler unit I8 by pipes 8land 82, respectively.

The radiator 18 serves to raise the dry bul temperature of the airmixture above that of the room, so that when the lmixture is introducedinto the room, it will not result in discomfort to the occupants. Forexample, in a case where the rooms are maintained at a dry bulbtemperature approximating 72 F. by or in conjunction with a suitableheating system, we have found that it is desirable to temper thehumidied air' to a temperature ranging between 79 F. and 85 F. It i`s tobe understood that, While we have elected to disclose in the preferredembodiment of our method, the step of heating the room space by aconventional heating method and the step of merely tempering Aor raisingthe temperature of the humidied mixture prior to entering the room, ourinvention in all of its aspects is not to be considered as vbeing solimited; for, in so far as certain ofthe broader aspects of our methodare concerned, all of the heating of the humidied mixture and the airinthe room may be effected either by the conventional room heatingequipment or by a unit like the radiator 18 of suii'icient capacity andarranged in the path of the air coming from the humidifier.

The structure shown in Figs. 1, 2, and 3 and as just described operatesto perform the several steps of our improved method and will maintain inthe room space I0 properhumidity values,

without the objectionable deposition of moisture I on the window panesand Without any deposition of moisture on lthe ceilings or walls of theroom` A Space. y

The temperature of the v-inside surfaces of the4 mains at asubstantially uniform value. depend- The rotating element 69 is suittheinside surfaces of the windows and similarlyA affected surfaces when thetemperature of these surfaces is below the dewpoint temperature of theair in the room space.

The amount of moisture which air Will take up 1 in passing through ahumidifier of the type shown varies directly as a function of the drybulb temperature of such air before entering the humidier. With theblower 61 operating at a constant rate of 'speed and with the dampers 53at fixed positions, xed proportions of room air and outdoor air willflow into the mixing inlet chamber 38, and this mixture will passthrough the humidifying chamber 56 at a substantially uniform volumerate. The dry bulb temperature of the mixture inthe chamber 38 is aresultant of the dry bulb temperature of its room air constituent andits outdoor air constituent, and therefore varies directly as a functionof the changing outdoor dry bulb temperature.A Therefore, with thehumidifying characteristics of the sprays being xed and the volumerate'of air flow through the sprays and eliminator being fixed, theamount of moisture added to the mixture will vary directly `as afunction of the dry bulb temperature of the outdoor air. We have foundthat vmoisture will be added tc the mixture in amounts which are asubstantially xed part of the diiference between the amount of moisturein the mixture,

prior to entering the humidifying chamber 56 and the amount the mixturecould hold were it saturated at its wet bulb temperature. Thehumidifying efficiency of the sprays and eliminator is the relationshipbetween the amount added to the mixture and the amount the mixture couldhold were it saturated at its wet bulb temperature.

The measure of the humidifying efficiency is the Value of theaforementioned part by which the moisture content of the mixture isincreased.

From' the above, it is apparent that, with the proportions of room andoutdoor air substantially constant and the humidifying efficiencysubstantially constant, and with the volume rate of air passing throughthe apparatus 30 and into the room substantially constant, the moisturecontent, and consequently the dewpoint temperature of the air in theroom, will vary directlyas afunction of the changing outdoor dry bulbtemperature and the inside window surface temperature.

Therefore, by predetermining and xingthe proportions of room'air andoutdoor air, the humidification efficiency, and the volume rate of airflow with respect to the humidilcation requirements of a particularhouse, the dewpoint temperature of the air in the rooms can be made tovary with the inside surface temperature of the windows and never exceeda point where objectionable condensation will occur on these surfaces.

It is to 'be noted that, according to ourmethod, the desired humiditycondition is maintained in the room, without objectionable condensation;and that this result is continuously and automatically obtained withoutthe necessity. of further changing the proportions of outdoor and roomair and the humidifying eiciency. AFor this rea-4 son, ourmethod has adistinct advantage over prior art humidifying methods using instrumentsand control systems to regulate the pro-- portions of room and outdoorair and/or to regulate the humidifying emciency. Such instruwindvelocities, and will vary slightly up or down ments and control systemsare lcostly and are at least of questionable durability and accuracy.

Fig. 5 of the drawings, is a graphl showing the actual results obtainedin a conventional dwelling house in the area around -New York city,wherein apparatus of the type shown in Figs. 1, 2 and 3 was installed.This house has a cubic foot capacity of approximately 25,000, and theapparatus was of a size to introduce into the room about 900 cubic feetofhumidied air per minute. It will be appreciated, of ceurse, that thecapacity of the apparatus will'be varied to suit the capacity andconditionsof the particular house where it is installed.

The dotted line curve inv Fig. l", shows the humidity values that can bemaintained in this house for the normal range of outside dry. bulbtemperatures during the heating season without condensation of moistureon the window panes. We have elected to call this curve the uallowablerelative humidity curve. This curve indicates the relation justexplained with normal outside on the graph between no wind conditionand' high Wind velocities, respectively.

In this particular house, the windows have single panes, and n'o stormwindows are installed. With storm windows, the allowable relative hu'-midity curve would be substantially the same shape as that shown, butwould be higher on the graph, as higher relative humidities could bemaintained inv the room spaces without condensation on the window,because of the resulting higher inside surface temperatures of the win--dows, the spaces between the storm windows and customary windows actingas a heat insu- 'lator from the outside dry bulb temperatures,

and also acting to nullify the effect of high wind velocities, whichproduce lower inside Window surface temperatures.

The full lin'e curve'on the graph indicates the mean actual humiditiesmaintained in this house during the heating season by following thesteps of our improved method. The curve shows the results obtainedwhenthe proportions of outside to inside air used were set at 1 to 3 andthe efficiency of the humidifying chamber was approximately 40%, that isto say, when the humidifying chamber added to the air 40% of thedference between the absolute humidityof the mixture prior to enteringthe chamber and the absolute humidity of the mixture if saturated at itswet bulb temperature.

From an examination of Fig. 5, it will be observed that for temperaturesbelow 20 above 0 F., the relative humidities maintained were 30% andslightly less, and that the curve show- 'ing the actual relativehumidities maintained in the room crossesthe allowable relative humiditycurve at 10 above 0 F. Therefore, for temperathe accepted optimum of 30%relative humidity was maintained; and for temperatures below 10 above 0F. a slight fog or frost appeared on the window panes, butnot to such anextent as to cause moisture to run down the window pane and result inpuddles. t"

Variations of tle actual relative humidity curve were obtained byusingdifferent proportions of foutside and inside airand using a difmiditycurve; but, in so doing, the amount of fresh air added to the roomswould, of course,

increase the heating load on the house. It was.

also found that if the efciency of the humidifying chamber were raisedto 60%'with a 1 to 3 proportion of outside and inside air, the actual frelative humidity curve would be approximately the same shape as the oneshown, but would cross the-allowable relative humidity curve ata higheroutside dry bulb temperature. Frost appeared on the. windows at a higheroutside the humidifying Veilciency may be selected to' maintain the`humidity condition desired by the .occupants of a particular house, and,when once determined, such humidity condition will be maintainedautomatically in the manner heretofore explained. The adjustments may besuch that the relative humidity of the air at the house is maintainedwithin the optimum range of 30% to 70%, and the deposition of moistureon the window panes will not be objectionable at the low temperatures.We have found that in reality it is not absolutely necessary, in orderto have a refreshing and healthful condition, for the relative humiditytobe maintained at a minimum of 30%. Therefore, in cases where theoccupants do not like to have a deposition of fog or frost on the windowat thev low 4temperatures the adjustment may be such that proper, orhealthful and` refreshing humidity conditions may be secured without thedeposition of moisture in the form of frostor fog. The operation andrange of results and conditions indicated on the graph in Fig. 5 areconsidered by us to be satisfactory. However, asjust explained,in accordance with our method they may be varied to `suit the conditions andthe particular desires of.

our improved method also keeps the air in motion in the room spaces andmaintains therein an even and positive supply of clean and fresh airwithoutv objectionable drafts.' The `room spaces are kept under a slightpositive pressure,

I due to the fact that more' air is supplied than is withdrawn, and thiscondition tends to prevent the entrance of dust and dirt from theoutside through cracks and crevices around `the windows and'doors in thehouse. The latter, in conjunction with the cleansing of all of the airsupplied to theroom, keeps the room spaces relatively room spaces isconcerned, there is a decided advantage over methods not employingpositive ventilation, `for in houses Where the amount of fresh airsupplied depends upon the infiltration of outside air through cracks(around windows and doors, too much air is supplied when there are highwind velocities on the outside and too little ventilation is providedwhen there is4 no wind.

In Fig. 4 of the drawings, we have shown an alternative form ofapparatus which performs the several steps of our improved method pre'viously explained. The apparatus is indicated by the reference numeral|00 and comprises a casing IDI suspended from the basement ceiling. Atone end of the casing is provided a pair of clean. In so far as thefresh air condition of the municate respectively with the outside airand with the room spaces. The ducts |02 and |03 are provided withdampers |04 and |05 respectively, which serve to properly proportion theamounts of outside air and room air drawn into the casing ing |0| isprovided three air supply ducts, which are indicated by the referencecharacter |06 andare Aadapted to be connected to grille-covered openingsin the oor of a room space in the same manner as the ducts of thepreviously described apparatus. A

The fresh air inlet duct |02 and the recirculating air duct |03communicate with an air inlet chamber |01 provided in the adjacent endof the casing |0|, which'chamber serves to mix the room air and freshair. The side ofthe chamber lute humidity of the mixture prior toentering the chamber and the absolute humidity of the mixture ifsaturated at its wet bulb temperature.

Humidificationis effected by a` plurality of water nozzles I arranged inthe chamber 0 and supplied with water from a suitable pipe 2 connectedtothe city water supply. The nozzles |I| are of the type which provide avery small, high velocity stream of water which strikes a surface of asuitable breaker plate and as a result the stream is broken up intominute particles which fill the chamber ||0 and are taken up by the airstream flowing through the chamber H0.

The breaker plates against which the jets Aof Water strike are indicatedby the reference character H3, there beingone plate for each jet.

The plates ||3 are secured to the ends of arms ||4 which are carried bya rotatable shaft ||5 A suitably journalled in the sidewalls of thecasing |0|. `A lever ,H6 is provided for rotating the shaft and forpositioning the plates ||3 with respect to the jets. istics and hencethe humidifying efficiency of the chamber l0 may be varied by rotatingthe shaft ||5 and thereby varying the angle at which streams of waterstrike the plates and the distances between the plates and the nozzles.-

Disposed across the side of the humidifying chamber I0 opposite to thefilter |08 is an evaporater-eliminatorV |20 which is constructed andfunctions in a manner similar to the evaporatoreliminator 60 of thepreviously described apparatus. The eliminator |20 performs thefunctions of eliminating'any free moisture entrained in the air mixtureowing from the chamber ||0 and of promoting evaporation of :moisture andthe humidication of such air mixture.

Behind the evaporator is arranged a motor blower unit |25 whichcomprises a motor 26 hav- I3 which receive the humidifled air mixtureflowing through the eliminator |20, and without- At the opposite end ofthe casi portions respectively, of the radiator.

meral |36.

The humidifying characterlets which are in communication with an airtempering chamber |33.

A suitable steam or hot Water radiator |34 is installed lin the airtempering chamber |33 and functions to raise the temperature of the airmixture to a point'where its entrance into the room spaces will not beuncomfortable to the occupants. For the purpose 'of preventing eddyingof the air flowing from the blowers and through the radiator, asplittervane |35 is provided which divides the flow of the air as itvcomes-'from the blower and directs it to the upper and lower Theopposite surfaces of the splitter vane, as well as the inside surfacesof the casing defining the tempering chamber, are lined with a soundabsorbing material 'indicated by the reference nu- As was the case oftheapparatus 30 shown in Figs. l, 2 and 3, the apparatus |00 withdraws apredetermined xed amount-of air per unit of time from the room spacesand takes in a predetermined fixed amount of air per unit of time fromthe atmosphere. The air from both sources is mixed, filtered, and passedthrough a humidifying chamber which adds to the air moisture inamountswhich area predetermined fixed part of the difference between theabsolute humidity .of the mixture prior to being humidifed and theabsolute humidity of the mixture were it saturated at its wet bulbtemperature. The temperature of the humidified mixture is then raised bypassing through a radiator and the air is then forced into the roomspace.

What we claim and desire to secure by Letters Patent of the UnitedStates is:

1. A/method of conditioning air in a room space during the heatingseason, without objectionable condensation on those internal roomsurfaces which are more readily aiected by changes in outdoor dry bulbtemperature, which comprises mixing substantially unvarying proportionsof thermally and hygrometrically untreated outdoor air and air ofsubstantially xed dry bulb temperature drawn from the room space;passing such mixture at its resultant mean dry bulbV temperature and ata substanv tially fixed volume rate through a humidifying zone having asubstantially xed humidifying eiciency; and introducing the humidiiiedmixture into the room space, so that the dewpoint temperature of the airin the room space varies directly as a function of the changing outdoorvdry bulb temperature; the substantially fixed values of theproportionate amounts of room and outdoorl air, the volume rate of theair mixture, and the hurnidifying efficiency of the zone beingsojrelated to one another and to the humidiflcation requirements of theroom space, that the dewpoint temperature of the air in the room spacedoes not exceed a point where objectionable condensation would occur onsaid internal room surfaces.

2. A method of conditioning air in aroom space during the heatingseason, without objectionable condensation on those internal roomsurfaces which are more readily affected by changes in outdoor dry bulbtemperature, which comprises heating the air in the room space toprovide a desired comfort condition; mixing substantially unvaryingproportions of thermally and hygrometrically untreated outdoor air andheated air from. the room space; passing such mixture at its resultantmean dry bulb temperature and at a substantially fixed volume ratethrough a humidifying zone ciency; and introducing the humidifiedmixture into the room space so thatithe dewpointI temperature of the airin the room space varies directly as a function of the changing outdoordry bulb temperature; the substantially fixed values of theproportionate amounts of room and outdoorair, the volume rate of the airmixture, and

' the humidifying eiliciency of the zone being so related to one anotherand tothe humidiflcation requirements of the room space, that thedewpoint temperature of the air in the roo`m space does not exceed apoint Where objectionable condensation would occur on saidinternalsurfaces.

3. A method of conditioning air ina room space during the heatingseason, Without objectionable condensation on those internal roomsurfaces whichare more readily affected by changes in outdoor dry bulbtemperature, which comprises heating the air in the room space toprovide a desired comfort condition; mixing substantially 'unvaryingproportions of thermally and hygrometricall'y untreated outdoor air andheated .air

l midifying zone having a substantially fixed hu.

from thefroom space; passing such mixture at its resultant mean dry bulbtemperature and V at a substantially xedvolume rate through ahumidifying eiliciency; increasing the dry bulb temperature of thehumidified mixture above that of the air in the room space; andintroducing the humidied mixturev into the room space so -that thedewpoint temperature of the air in the room space varies directly as afunction of the changing outdoor dry bulb temperature; the substantiallyfixed values of the proportionate amounts of room and outdoorl air, thevolume rate of the air mixture,- and the humidifying' efliciency of thezone being so related to one another and to the humidication,requirements of the room space, that the dewpoint temperature of the airhaving a substantially lixetl humidifying eiliits resultant mean drybulb temperature and at a substantially fixed volume rate through ahumidifying zone having a substantially fixed humidifying efllciency;and introducing the humidied mixture into the room space so that thedewpoint temperature of the air in the room space varies directly as afunction of the changing outwhich are more readily affected by changesin outdoor dry bulb temperature, which comprises establishing andmaintaining a stream of air iiowing at a' substantially xed volume rateand composed of substantially fixed proportions of thermally andhygrometrically untreated outdoor air, and air of substantially fixeddry bulb temperature drawn from the room space; continually increasingthe moisture content of such air stream by an amount which is equal to asubstantially fixed part of the difference' between the amount ofmoisture the air stream contains before its moisture content isincreased and the amount of moisture the air stream could hold were itsaturated at its wet bulb temperature;

l introducing the humidified stream into the lroom `space, so that thedewpoint temperature of the airv in the room space varies directly as afu'ncjr tion of the changing outdoor dry bulb temperature; thesubstantially fixed values of the proportionate amounts of room andoutdoor air ccmposlng the air stream, of the volume rate ofthe airstream, and of the part by which the moisture content of the air streamis increased, being so related to one another and to the humidificationrequirements of the room space, that the dewpoint `temperature of theair in the room space does not exceed a point where objectionablecondensation would occur on said internal room surfaces.

` FOWLER MANNING.

ROBERT D. LAMBERT.

